Biological two-stage contaminated water treatment system and process

ABSTRACT

The systems and methods may be used for treatment of water that contains contaminants. Water containing at least one of a nitrate, percholate, chromate, selenite, and a volatile organic chemical is combined with nutrients and then is processed in an anoxic-anaerobic bioreactor. The combined effluent may also be oxygenated by dosing with hydrogen peroxide or liquid oxygen. The combined effluent of the bioreactor is dosed with a particle conditioning agent. The combined effluent treated water of the bioreactor is then filtered in a biofilter to produce a treated effluent stream. The influent water and combined effluent of the anoxic-anaerobic bioreactor may also be dosed with hydrogen peroxide to control biomass content in the system.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority as a continuation-in-part of U.S.patent application Ser. No. 13/573,533, filed on Sep. 22, 2012, theentire contents of which are herein incorporated by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to processes and systems for treatment ofgroundwater or surface water that contains at least one of the followingcontaminants: nitrate, perchlorate, chromate, selenate, and volatileorganic chemicals such as perchloroethylene, trichloroethylene,dichloroethylene, vinyl chloride, trichloropropanol,dibromochloropropane, and carbon tetrachloride. The new methodimplements a second treatment stage aerobic biofilter in combinationwith a first stage anoxic/anaerobic bioreactor with interstageoxygenation and particle conditioning addition.

Description of the Related Art

Raw drinking water sources may contain nitrate, perchlorate, chromate,selenate, and one or more of various volatile organic chemicals, forexample, perchloroethylene, trichloroethylene, dichloroethlyene, vinylchloride, trichloropropane, dibromochloropropane and carbontetrachloride. There are numerous processes and technologies availablefor removing one or more of these contaminants from drinking water,including ion exchange, reverse osmosis, electrodialysis reversal,granular activated carbon adsorption, air stripping, and advancedoxidation. Each of these processes and technologies has one or more ofthe following disadvantages: exerts a high energy demand, exerts a highoperational cost, generates of a high-strength concentrated waste streamthat must be further treated or disposed, adds considerable salt to agiven watershed, does not address all of the cited contaminants, issensitive to raw water quality, and sensitive to operating conditions.

Various biological processes have also been tested and used to treat oneor more of the cited contaminants. These processes are typically singlestage biological reactors with upstream nutrient addition. Theseprocesses have one of more of the following disadvantages in that they:cannot treat all of the cited contaminants, produce excess biomass thatcan slough into the effluent of the bioreactor, can experience cloggingdue to the production of excessive extracellular polymeric substances,and can leak nutrients into the effluent, thereby causing biologicalregrowth potential and disinfection by-product formation potential.

Some processes may include an additional element with a particulatefilter unit that may be sand, granular activated carbon, anthracite orsimilar media and may have a backwash system to reduce clogging and tofluidize the bioreactor bed. However, the filtration in these systems isfor high rate particle filtration rather than for degrading and removingdissolved contaminants.

SUMMARY OF THE INVENTION

In one preferred and non-limiting embodiment, provided are processes andsystems for treatment of water that contains contaminants. Watercontaining at least one of a nitrate, percholate, chromate, selenate anda volatile organic chemical is combined with nutrients and then isprocessed in an anoxic-anaerobic bioreactor. The combined effluent ofthe bioreactor is dosed with a particle conditioning agent. The combinedeffluent may also be oxygenated by dosing with hydrogen peroxide orliquid oxygen. The combined effluent treated water of the bioreactor isthen filtered in a biofilter to produce a treated effluent stream. Theinfluent water and combined effluent of the anoxic-anaerobic bioreactormay also be dosed with hydrogen peroxide to control biomass content inthe system.

In another preferred and non-limiting embodiment, provided is a methodfor treatment of water that contains contaminants including: dosing aninfluent water stream containing at least one of a nitrate, perchlorate,chromate, selenite, and a volatile organic chemical with a dosing amountof one or more nutrients; processing the combined influent water streamin an anoxic-anaerobic bioreactor; dosing an effluent treated waterstream of the anoxic-anaerobic bioreactor with a dosing amount of aparticle conditioning agent; oxygenating the effluent treated waterstream of the anoxic-anaerobic bioreactor; and filtering the combinedeffluent treated water in an aerobic biofilter to produce a treatedeffluent stream, wherein the dosing amount of the of one or morenutrients and the dosing amount of the particle conditioning agent areperiodically adjusted by a program logic controller.

In a further preferred and non-limiting embodiment, provided is a systemfor treatment of water that contains contaminants including: ananoxic-anaerobic bioreactor in fluid communication with an influentwater source containing at least one of a nitrate, perchlorate,chromate, selenite, and a volatile organic chemical; a nutrient dosingunit in fluid communication with said influent water source, whereinsaid nutrient dosing unit is controlled by a program logic controller; aparticle conditioning dosing unit in fluid communication with aneffluent treated water conduit connected between said anoxic-anaerobicbioreactor and an aerobic biofilter, wherein said particle conditioningdosing unit is controlled by said program logic controller; a treatedeffluent output of said aerobic biofilter; a plurality of in-linesensors positioned to collect data related to the influent water source,effluent treated water, and treated effluent, the sensors in electroniccommunication with the program logic controller, wherein the programlogic controller is programmed to control the nutrient dosing unit andparticle conditioning dosing unit based at least partially upon datareceived from the in-line sensors.

These and other features and characteristics of the present invention,as well as the methods of operation and functions of the relatedelements of structures and the combination of parts and economies ofmanufacture, will become more apparent upon consideration of thefollowing description and the appended claims with reference to theaccompanying drawings, all of which form a part of this specification,wherein like reference numerals designate corresponding parts in thevarious figures. It is to be expressly understood, however, that thedrawings are for the purpose of illustration and description only andare not intended as a definition of the limits of the invention. As usedin the specification and the claims, the singular form of “a”, “an”, and“the” include plural referents unless the context clearly dictatesotherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flow diagram of one embodiment of a biologicaltwo-stage contaminated water treatment system and process according tothe principles of the present invention; and

FIG. 2 is a schematic flow diagram of an embodiment of anotherembodiment of biological two-stage contaminated water treatment systemand process according to the principles of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following detailed description represents the best currentlycontemplated modes for carrying out the invention. The description isnot to be taken in a limiting sense, but is made merely for the purposeof illustrating the general principles of the invention. For purposes ofthe description hereinafter, the terms “end”, “upper”, “lower”, “right”,“left”, “vertical”, “horizontal”, “top”, “bottom”, “lateral”,“longitudinal” and derivatives thereof shall relate to the invention asit is oriented in the drawing figures. However, it is to be understoodthat the invention may assume various alternative variations and stepsequences, except where expressly specified to the contrary. It is alsoto be understood that the specific devices and processes illustrated inthe attached drawings, and described in the following specification, aresimply exemplary embodiments of the invention. Hence, specificdimensions and other physical characteristics related to the embodimentsdisclosed herein are not to be considered as limiting.

Referring to FIG. 1, a biological treatment system 10 for removing oneor more contaminants from groundwater or surface water has a first stagebioreactor 12 and a second stage biofilter 14. The bioreactor 12 may bean anoxic-anaerobic bioreactor that receives influent raw drinking water20 with nutrients 22 added. The nutrients 22 may include acetic acid,ethanol, and glycerin as carbon source/electron donors, phosphorus inthe form of phosphoric acid, and nitrogen in the form of ammonia mayserve to achieve microbial degradation of water contaminants that mayinclude nitrate, perchlorate, chromate, selenate, perchloroethylene,trichloroethylene, trichloropropane, carbon tetrachloride,dibromochloropropane and other volatile organic chemicals. Bacteriaacross the bioreactor can reduce dissolved oxygen, nitrate, andperchlorate to water, nitrogen gas, and chloride, respectively. Aceticacid is oxidized to carbon dioxide. The dosing of the influent waterwith hydrogen peroxide 24 may limit biological clogging of the system10. As explained below, dosing of the nutrients 22 can be controlled andregulated by a program logic control system 50 which periodically and/orcontinuously receives measurements from a variety of in-line sensorspositioned throughout the system 10.

The bioreactor 12 may be a suspended growth reactor, granular fixed-filmreactor that is fixed-bed or fluidized bed, or membrane-based fixed-filmreactors. The anoxic-anaerobic bioreactor 12 may degrade/remove nitrate,perchlorate, chromate, selenate, perchloroethylene, trichloroethylene,dichloroethylene, vinyl chloride, trichloropropanol, carbontetrachloride, and other volatile organic chemicals. In somenon-limiting embodiments, the bioreactor 12 may be a steel pressurevessel containing granular activated carbon (GAC). The pressure vesselcan have various dimensions, and the GAC can be colonized by organismsindigenous to the raw water. In one non-limiting embodiments, thebioreactor contains approximately five feet of GAC.

After the dosed water influent stream 26 is treated across thebioreactor 12 the effluent treated water 30 may be dosed with oxygen 32and dosed with a particle conditioning agent 34 in the interstage flowbetween the bioreactor 12 and the aerobic biofilter 14. The oxygenation32 may be accomplished by dosing with hydrogen peroxide 24, liquidoxygen, by an aeration process such as fine-bubble diffusion or cascadeaeration, or by an education process. The particle conditioning agent 34dosing may be by use of a coagulant such as alum or ferric, or by use ofa polymeric compound such as cationic polymer. The dosage of hydrogenperoxide 24 may be approximately 1 to 2 mg/L for biomass control andapproximately 10 to 12 mg/L for oxygenation. Dosing with cationicpolymer can improve filterability of the sloughed cells and hydrogenperoxide can reoxygenate the water and provide some oxidizing power toeliminate acetic acid or hydrogen sulfide if either of these compoundsremains. Dosing can vary depending on the performance of the system 10.Program logic control system 50 can be used to control dosing of oxygen32 and/or particle conditioning agent 34 based on information aboutsystem performance gathered using in-line sensors located throughout thesystem 10. A de-gas stage may be included upstream of the dosing of theparticle conditioning agent 34 and oxygen 32 if nitrogen gas bubblescause hydraulic or turbidity challenges in the biofilter 14. De-gassingcould be achieved by using an open basin, open channel cascading flow,or a mechanical gas separator. If head is broken for the de-gas step, aninterstage pump can be added.

The effluent treated water 30 with added dosing in the interstage flowthat may increase the oxidation-reduction potential of the water,release trapped nitrogen gas bubbles as necessary, and conditionsloughed biomass is then processed in the aerobic biofilter 14. Theaerobic biofilter 14 may be a granular media-based biofilter or abiologically active membrane filter. The aerobic biofilter 14 maydegrade/remove remaining volatile organic chemicals, hydrogen sulfide,residual carbon nutrient (including residual acetic acid), and sloughedbiomass. The aerobic biofilter 14 may be a steel pressure vessel.

The system 10 control of biomass conditions in the anoxic-anaerobicbioreactor 12 and the aerobic biofilter 14 are important to theefficiency of removing the contaminants in the influent water 20 and inthe effluent treated water 30. The contaminants in the influent water20, the nutrients 22 from nutrient dosing, and the constituents in theresulting effluent treated water 30 are further treated in the aerobicbiofilter 14. The biomass conditions at each stage 12, 14 may bemonitored for turbidity and pressure loss to measure slime, sloughing,clogging and the like conditions. The dosing of influent water 20 andeffluent treated water 30 with hydrogen peroxide 24 serves to chemicallyscour biomass and unclog the bioreactor 12 and biofilter 14, and theconduit or piping for conducting fluids in the system 10. The hydrogenperoxide 24 may be dosed intermittently or continuously as controlled bya program logic control system 50. There may also be a backwash pump 40and backwash tank 42 to control or minimize biomass in the system 10 toreduce biological clogging of the bioreactor 12 and biofilter 14.Backwashes can be initiated automatically based on time and can includean air scour step, a combined air scour/fluidization step, and a finalfluidization step.

The two-stage system 10 with a wide range in oxidation-reductionpotential allows enhanced processing of the range of contaminants thatcan be degraded and removed. The destruction of multiple contaminantsmay be accomplished with reduced energy input and without producinghigh-volume, high-strength waste streams. The contaminant removalperformance has been demonstrated in analysis to be typicallyindependent of raw water quality. The treated effluent stream 38 of thesystem 10 also has minimal biomass. However, the treated effluent stream38 can be dosed with a disinfection agent, such as chlorine, to meet atarget residual level prior to storage and/or distribution. Disinfectionagent dosing preferably occurs at a point downstream of the backwashdraw to avoid circulating disinfection agent to the bioreactor 12 and/orbiofilter 14 as part of the backwash process.

Run times for the bioreactor 12 and biofilter 14 can vary, but aretypically about 24 and 48 hours, respectively. These values can beadjusted up or down based on start-up performance. The bioreactor 12and/or biofilter 14 are expected to be offline for approximately 30minutes during a backwash procedure. Redundancy in system 10 components(such as the use of multiple bioreactors and/or biofilters) can beconsidered to maintain continuous service during backwash andmaintenance periods as necessary.

In-line sensors and other analytical equipment may be positionedthroughout the system 10 to monitor system performance and gather datathat can be used to control dosing and other operations. For example,flow rates can be monitored throughout the system 10, including the flowrates of the influent raw drinking water 20, influent stream 26,effluent treated water 30, and treated effluent stream 38. The headlossacross the bioreactor 12 and biofilter 14 can also be determined bymeasuring and comparing pressure data from either side of the bioreactor12 and biofilter 14. Run time can also be monitored. Dissolved oxygenconcentration, nitrate concentration, perchlorate concentration,turbidity, and chlorine concentration at various points can also bemeasured. For example, the dissolved oxygen concentration, nitrateconcentration, perchlorate concentration, turbidity, and chlorineconcentration in the influent raw drinking water 20, the influent stream26, the effluent treated water 30, and the treated effluent stream 38can be measured and monitored, either continuously or periodically,using an in-line probe, capillary electrophoresis analyzer (lab on achip), ion chromatograph, or other suitable analytical equipment.

By way of further example, oxygen analyzers 52, 53 and nitrate analyzers54, 55 can be used to measure the dissolved oxygen and nitrate in theraw drinking water 20 and effluent treated water 30. Pressure sensors56, 57, 58 may be used to gather pressure data at various points in thesystem. Turbidity sensors 59, 60 may be used to measure turbidity of theeffluent treated water 30 and treated effluent stream 38.

The gathered data can be transmitted to the program logic control system50. The program logic control system 50 can then use the received datato control various aspects of the system 10, allowing for a fullyautomated biological treatment process. For example, during operation,data received by the program logic controller 50 can be used to controldosing at the various stages of the system 10, allowing for the dosingamounts to be modified automatically in view of the actual, measuredconditions within the system 10.

Program logic control system 50 can be configured, programmed, oradapted or otherwise used to control the dosing of nutrients 22 andother additives to the influent raw drinking water 20. For example,program logic control system 50 can be programmed to calculate a targetamount of nutrients 22, oxygen 32, particle conditioning agents 34,and/or other dosing additives based on measured data concerning theinfluent raw drinking water 20, such as the flow rate, as well as theconcentration of the stock solution of the various dosing additives.These target values can be set based on empirical data gathered duringthe start-up of the system 10 and predictive modelling of how the system10 should behave. The program logic control system 50 can then send acontrol signal to the dosing units 70, 72 associated with each additiveto deliver the appropriate dose. By way of further explanation, theappropriate concentration of nutrients 22 can be calculated by programlogic control system 50 as a function of the dissolved oxygen andnitrate concentrations in the raw drinking water 20. Data received fromthe oxygen analyzers 52, 53 and/or nitrate analyzers 54, 55 can becorrelated with other information, such as the flow rate and/or stocksolution concentration, to determine the dosing amount and a controlsignal can be sent to nutrient 22 dosing unit 70 or feed pump to dose atthe calculated concentration. The program logic control system 50 canalso be programmed with a range of dissolved oxygen and nitrateconcentrations that are desired for the effluent treated water 30, andwhen the measured values (as gathered by in-line sensors) are determinedto be outside of these ranges, the program logic control system 50 canadjust the dosing of nutrients 22 to correct the concentrations. Thisfeed-forward, feed-backward nutrient 22 dose control ensures thatsufficient nutrients 22 are dosed while minimizing excess nutrients inthe effluent treated water 30 of the anoxic-anaerobic bioreactor 12.

By way of another example, pressure and turbidity data gathered bypressure sensors 56, 57, 58 and/or turbidity sensors 59, 60 can betransmitted to the program logic control system 50 for calculatingbiomass conditions at each stage 12, 14 to assess the slime growth,sloughing matter, clogging and the like that is detrimental to efficientsystem 10 operation. Based on the measured data, the program logiccontrol system 50 can then adjust the dosing of, e.g., hydrogen peroxide24 by control of a hydrogen peroxide dosing unit 72 in water flows 26,30, and/or control backwash pump 40 and air blower 18 to chemicallyscour and physical loosen and remove biomass accumulation in the system10. The measured data may also be used to control and adjust dosing ofthe particle conditioning agent 34 by a particle conditioning dosingunit 74 and of the liquid oxygen 32 by an oxygen dosing unit 76. Furtherspecifics of exemplary feed-forward, feed-backward control loops thatcan be implement in the system 10 follow.

A feed-forward, feed-backward control loop implemented by program logiccontrol system 50 can be used to determine nutrient 22 dosing of the rawdrinking water 20. In one embodiment, dosing of an electron donor feedchemical, such as acetic acid, can be controlled using a feed-forward,feed-backward control loop implemented by the program logic controlsystem 50. The dose of the electron donor feed chemical can bedetermined based on the following general formula:Dose in mg/L={ED1}+{ED2}where {ED1} represents the dose determined from the feed-forward portionof the control loop and {ED2} represents the dose determined from thefeed-backward portion of the control loop.

The feed-forward dose {ED1} can be a function of the concentrations ofdissolved oxygen and nitrate in the raw drinking water 20. Data on thedissolved oxygen and nitrate concentrations can be measured duringstartup using in-line sensors, and these measurements may becontinuously or periodically repeated during operation to provideupdated data to the program logic control system 50. The feed-forwarddose {ED1} can then be determined using this data according to one ormore equations programmed into program logic control system 50. Theseequations can be derived a number of different ways, including by halfreaction techniques, or through the analysis of empirical data. By wayof example, one or more of the following formulas may be useful indetermining the feed-forward portion of the dose of acetic acid {AA1}:{AA1}=C ₁*O₂ +C ₂*NO₃ (half reaction based){AA1}=C ₃*(C ₄*O₂ +C ₅*NO₃) (empirical based)wherein {AA1} is the acetic acid dose in mg/L as CH₃COOH, O₂ is themeasured dissolved oxygen in the raw drinking water in mg/L, NO₃ is themeasured nitrate concentration in the raw drinking water in mg/L as NO₃,and C₁ through C₅ are derived constants. In one embodiment, C₁=1.54,C₂=0.99, C₃=1.7, C₄=0.38, and C₅=0.24. For electron donor feed chemicalsother than acetic acid, a similar control strategy can be used withdifferent control equations that are based on an electron donorequivalency to acetic acid.

The feed-backward dose value {ED2} can be determined by program logiccontrol system 50 using data collected through downstream sampling andcan have the effect of either increasing or decreasing the overalldosing of electron donor feed chemical to the influent raw drinkingwater 20. By way of example, the feed-backward dose {ED2} can bedetermined by monitoring the nitrogen concentration (as NO₂ and/or NO₃)in the interstage effluent treated water 30 using the sensors discussedherein and then comparing, at the program logic control system 50, themeasured value(s) to a target or set point nitrogen concentration.Deviations between the measured value and the target value can then befactored into the calculation of {ED2}. Thus, the dosing of the influentraw drinking water 20 is a function of the downstream performance of thesystem 10. By way of another example, feed-backward dose {ED2} can bedetermined by monitoring the perchlorate concentration in the effluenttreated water 30 and/or treated effluent stream 38 using the sensorsdiscussed herein and then comparing, at the program logic control system50, the measured value(s) to a target or set point value. Deviationsbetween the measured perchlorate concentration and the setpoint can befactored into a determination of the appropriate dosing of the electrondonor feed chemical in the influent raw drinking water 20.

Once the electron donor feed chemical dose is determined, program logiccontrol system 50 can send a control signal to nutrient dosing unit 70to dispense the appropriate dose of electron donor feed chemical.Throughout operation, the dosing signal can be modified as additionalgathered data is received and analyzed by the program logic controlsystem 50. Dosing of other nutrients 22 can be controlled by programlogic control system 50 as well. For example, the dosing of phosphorus,such as in the form of phosphoric acid, to the influent raw drinkingwater 20 can be determined as a function of the electron donor feedchemical according to the following formula:Phosphoric acid dose (in mg/L as P)=C ₆*{ED}where C₆ is a derived constant and {ED} is the dose of electron donorfeed chemical in mg/L. When {ED} is acetic acid, it has been found thata preferred value of C₆ is 0.011.

Also useful is the control of dissolved oxygen in the treated effluentstream 38, which can be accomplished by adjusting the dosing of oxygen32 in the effluent treated water 30 through a feedback controlmechanism. For example, an oxygen analyzer can be used to monitor thedissolved oxygen concentration in the treated effluent stream 38. Thismeasured value can be provided to the program logic control system 50where it can be used to determine the dosing of oxygen 32 to theeffluent treated water 30 according to the following formula:Oxygen (in mg/L)=C ₇*{DO_(target)}where C₇ is a derived constant and {DO_(target)} is the target setpointof the dissolved oxygen concentration in mg/L in the treated effluentstream 38. When the oxygen 32 is supplied in the form of H₂O₂, it hasbeen found that a preferred initial value of C₇ is 2.5, though this canbe adjusted. A feed-backward control mechanism can then be used toadjust the supply of oxygen 32 based on the measured value of thedissolved oxygen concentration in the treated effluent stream 38. If,for example, the measured value of dissolved oxygen in the treatedeffluent stream 38 is not within an acceptable deviation from the targetDO setpoint over a proscribed period of time, the dose of oxygen 32supplied to the effluent treated water 30 can be adjusted. Minimum andmaximum oxygen doses can also be set by an operator.

Program logic control system 50 can also be configured or programmed tomanage headloss across each bioreactor 12, 14. Management of headlosscan be accomplished in a variety of different ways, and generallyinvolves measuring the headloss across the media bed and underdrain ofthe bioreactor 12 or biofilter 14 over time. The headloss can bedetermined by measuring, using pressure sensors, the difference inpressure across the bioreactor 12 or biofilter 14. If the rate ofheadloss exceeds a predetermined rate, the operator can be notified andone or more headloss correction techniques can be initiated manually orautomatically.

One exemplary headloss correction technique involves increasing thehydrogen peroxide dosing to the backwash stream to scour the system ofbiomass, provided the increase does not exceed the maximum allowedabsolute dose. Another headloss correction technique involves initiatingan underdrain oxygen soak step as part of the backwash procedure. Yetanother headloss correction techniques involves reducing the amount oftime between backwashes. Another headloss correction technique involveschanging the air scour time and/or intensity during the backwashprocess. Yet another headloss correction technique involves dosing theinfluent raw drinking water 20 with hydrogen peroxide to scour thesystem of biomass.

Dosing of a disinfection agent, such as chlorine, to the treatedeffluent stream 38 can also be controlled by the program logic controlsystem 50 using a feed-forward, feed-backward control mechanism. Forexample, the feed rate of the disinfection agent can be set and/oradjusted based on a measured system flow rate at a point upstream of thedisinfection agent dosing point, such as the effluent treated water 38flow rate. The residual amount of disinfection agent can also bemeasured at a point downstream of the dose point and compared to aresidual setpoint. Dosing can then be adjusted upward or downward toaccount for differences between the measured residual value and thesetpoint value. Changes to the dosing amount can be tracked over timeand, if the required dose as determined based on the measured residualamount exceeds a predetermined value, the operator can be notified aboutpotential nitrite production/accumulation within the system 10.

As mentioned above, the bioreactor effluent treated water 30 may bedosed with a particle conditioning agent 34, such as a coagulant or apolymeric compound, in the interstage flow between the bioreactor 12 andthe aerobic biofilter 14 to control biomass sloughing. A dosing amountof the particle conditioning agent 34 can be determined and controlledby program logic control system 50 based on measured turbidity values.For example, the turbidity of the effluent treated water 38 can bemonitored using a turbidity sensor and the value can be reported to theprogram logic control system 50 where it is compared to a predeterminedsetpoint. If the measured turbidity differs from the setpoint by morethan a certain amount, the program logic control system 50 can increaseor decrease the dosing of the particle conditioning agent 34accordingly.

Exemplary Embodiments

In one preferred and non-limiting embodiment, and as discussed, thefixed-bed (FXB) biological process according to the present inventionrepresents two-stage conventional granular media filtration withadditional chemical feed points. In this embodiment, acetic acid andphosphoric acid are dosed to the raw water, which then passes through afixed-bed bioreactor, and the bioreactor includes a steel pressurevessel containing approximately 5 feet of granular activated carbon(GAC). The pressure vessel can be various dimensions, and the GAC iscolonized by organisms indigenous to the raw water. Bacteria across thebioreactor reduce dissolved oxygen (DO), nitrate, and perchlorate towater, nitrogen gas, and chloride, respectively. Acetic acid is oxidizedto carbon dioxide. Effluent from the bioreactor is dosed with cationicpolymer (to improve filterability of the sloughed cells) and hydrogenperoxide (which reoxygenates the water and provides some oxidizing powerto eliminate acetic acid or hydrogen sulfide if either of thesecompounds breakthrough). A degas step may be included upstream of thepolymer and peroxide if nitrogen gas bubbles cause hydraulic orturbidity challenges in the second stage bioreactor. Degas could beachieved by using an open basin, open channel cascading flow, or amechanical gas separator. If head is broken for the degas step, aninterstage pump could be used. After polymer and peroxide are dosed,water passes through a second FXB bioreactor (steel pressure vessel),which acts as an aerobic biofilter (to remove turbidity, andbiologically oxidize any residual acetic acid and hydrogen sulfide).Biofilter effluent is then disinfected and is ready for storage ordistribution.

In one preferred and non-limiting embodiment, and with respect to thein-line monitoring process, some or all of the following parameters aremeasured continuously using in-line sensors and analytical equipment:flow rate; bioreactor head loss; run time; dissolved oxygenconcentration (including raw water and biofilter effluent), such as byusing an in-line probe; nitrate concentration (including raw water andbioreactor effluent), such as by using an in-line probe or a capillaryelectrophoresis analyzer; perchlorate concentration (bioreactoreffluent), such as by using a capillary electrophoresis analyzer or anion chromatograph; and/or turbidity (including bioreactor effluent andbiofilter effluent); and chlorine concentration (downstream of chlorineaddition point).

In one preferred and non-limiting embodiment, the FXB biologicaltreatment process is fully automated, and the programmed logiccontroller (PLC) is configured or programmed to deliver a targetchemical dose based on flow rate and stock solution concentration. Thetarget dose for polymer, peroxide, and chlorine are fixed, and are basedon empirical data gathered during start-up. Dose set points can beadjusted up or down automatically if turbidity values or dissolvedoxygen concentrations in the biofilter effluent are outside a set range.In this embodiment, acetic and phosphoric acid chemical feed rates arealso a function of target dose and stock solution concentration. In thiscase however, the target dose fluctuates as a function of raw water DOand nitrate concentration. The PLC calculates a target acetic andphosphoric acid dose using an empirical formula and data from thein-line nitrate and DO analyzers. The PLC will also adjust the aceticand phosphoric acid dose, as necessary, if the nitrate or perchlorateconcentration in the bioreactor effluent fall outside a set range.

In one preferred and non-limiting embodiment, process times for the FXBbioreactor will be approximately 24 hours, and process times for theaerobic biofilter will be approximately 48 hours. These process timesmay be adjusted slightly up or down based on start-up performance.Further, backwashes will initiate automatically based on time, and willinclude an air scour step, a combined air scour/fluidization step, and afinal fluidization step, and no filter to waste period is anticipated. Abioreactor/biofilter is expected to be off line for approximately 30minutes during a backwash procedure. Redundancy can be considered tomaintain continuous service during backwash and maintenance periods asnecessary.

One preferred and non-limiting embodiment (as illustrated in FIG. 2)includes control loops or processes as follows:

Acetic Acid Control

1. Use of a combination feed forward and feed back to determine dose:(1) in mg/L CH₃COOH={AA1}+{AA2}Feed Forward1. Feed water electron donor dose (i.e., acetic acid dose (1)) iscontrolled by feed water dissolved oxygen concentration (2) and feedwater nitrate concentration (3):AA dose {AA1} (in mg/L as CH₃COOH)=1.54*O₂ (2) (in mg/L)+0.99*NO₃ (3)(in mg/L as NO₃) (half reaction based)AA dose {AA1} (in mg/L as CH₃COOH)=1.7*(0.38*O₂ (2) (in mg/L)+0.24*NO₃(3) (in mg/L as NO₃)) (empirically based)

For electron donor feed chemicals, other than acetic acid, similarcontrol strategy can be implemented with different control equationsbased on an electron donor equivalency to acetic acid.

Feed Backward

1. Feed water electron donor dose is trimmed {AA2} by stage 1 effluentnitrogen concentration (no. 2 and no. 3) compared to stage 1 effluentnitrogen concentration setpoint {S1}.

2. Optional control and monitoring of stage 1 (9) and/or stage 2 (17)effluent perchlorate concentration, such as through laboratory analysisor an automated analytical system.

Orthophosphate Control

Feed Forward

1. Feed water orthophosphate dose (i.e., phosphoric acid dose (4)) iscontrolled by feed water electron donor (acetic acid) dose (1):Phosphoric acid dose (4) (in mg/L as P)=0.011*acetic acid dosed (1)(mg/L as CH₃COOH)Effluent Dissolved Oxygen (DO) Control1. Biofilter effluent DO control includes monitoring DO at (12).2. Dose hydrogen peroxide in mg/L (6) based on the following formula:H₂O₂ in mg/L (6)=Target set point DO concentration in mg/L(12)*(adjustable parameter, initially 2.5)Feed Backward1. If (12) is not within an acceptable deviation from target oxygen setpoint for an operator adjustable period of time, modify hydrogenperoxide dose at (6) by an operator set adjustment amount in mg/L, wherethe minimum and maximum hydrogen peroxide doses to be operator set inmg/L.Bioreactor Headloss Management1. Hydrogen peroxide dose (14) to bioreactor backwash initially set atoperator set point in mg/L.Feed Backward1. Monitor headloss across bioreactor media bed and underdrain ((13),(14), and (15)) over time. If rate of headloss increase exceeds operatorentered rate over operator entered time period, initiate at least one ofthe following operator selectable options and notify operator: (a)increase backwash hydrogen peroxide dose (14) by operator entered amountin mg/L up to a maximum allowed absolute dose; (b) initiate underdrainhydrogen peroxide soak step as part of backwash procedure dosing at(14); (c) reduce run time set point between backwashes by operatorentered amount; (d) change air scour time and/or intensity duringbackwash; and/or (e) dose hydrogen peroxide at (5) at operator entereddose in mg/L.Chlorine Dosing and Demand Monitoring1. Chlorine is dosed for residual disinfection at (13) to meet a targetresidual at (18).Feed Forward1. Modify chlorine feed rate at (13) based on system flow rate.Feed Backward1. Dose chlorine at (13) based on residual measured at (18) to meetoperator entered chlorine residual set point, and increase dose to bewithin set deviation of set point.2. Monitor chlorine residual at (18), tracking dose (13) versus residual(18) over time. If required dose (13) changes more than operator enteredvalue to meet a target residual (18), and notify operator and/oractivate alarm indicating potential nitrite production/accumulation.Biomass Sloughing Control System1. Filter aid polymer is dosed at (10) to control biomass sloughingthrough removal in biofilter.Feed Backward1. Monitor turbidity (11). If turbidity exceeds operator entered value,increase or decrease polymer dose at (10) by operator entered value, andnotify operator.

As illustrated in FIG. 2, and as discussed above (and in one preferredand non-limiting embodiment), various specified sample points areprovided for use in controlling and executing the method and process,including, but not limited to: turbidity sample points (7) and (11);nitrate sample points (3) and (8); oxygen sample points (2) and (12);perchlorate sample points (9) and (17); chlorine sample points (18), andpressure monitoring points (13), (14), (15), and (16). In particular,and in this preferred and non-limiting embodiment, the level or datasensed or sampled at these sample points may be used in dosing,determining, calculating, adding, or injecting one or more of thefollowing compounds: acetic acid (1), phosphoric acid (4), H2O2 (5),(6), and (14) polymer (10), and/or chlorine (13). Further, and inanother preferred and non-limiting embodiment, and as discussed above,the process control methodology described above may be used incontrolling and effecting the water treatment system illustrated in FIG.1.

Although the invention has been described in detail for the purpose ofillustration based on what is currently considered to be the mostpractical and preferred embodiments, it is to be understood that suchdetail is solely for that purpose and that the invention is not limitedto the disclosed embodiments, but, on the contrary, is intended to covermodifications and equivalent arrangements that are within the spirit andscope of the appended claims. For example, it is to be understood thatthe present invention contemplates that, to the extent possible, one ormore features of any embodiment can be combined with one or morefeatures of any other embodiment.

What is claimed is:
 1. A method for treatment of water that contains contaminants comprising: dosing an influent water stream containing at least one of a nitrate, perchlorate, chromate, selenate, and a volatile organic chemical with a dosing amount of one or more nutrients; after dosing the influent water stream with the one or more nutrients, processing the influent water stream in an anoxic-anaerobic bioreactor; dosing an effluent treated water stream of the anoxic-anaerobic bioreactor with a dosing amount of a particle conditioning agent; oxygenating the effluent treated water stream of the anoxic-anaerobic bioreactor; and after dosing the effluent treated water stream with the particle conditioning agent and oxygenating the effluent treated water stream, filtering the effluent treated water stream in an aerobic biofilter to produce a treated effluent stream, monitoring, using one or more sensors, at least a measured dissolved oxygen content in the influent water stream, a measured dissolved oxygen content in the treated effluent stream, a measured nitrate content in the influent water stream, and a measured turbidity value in the effluent treated water stream, wherein the dosing amount of the of one or more nutrients, the dosing amount of the particle conditioning agent, and the oxygenating of the effluent treated water stream are periodically adjusted by a program logic controller based upon data received from the one or more sensors, wherein the dosing amount of the one or more nutrients is adjusted by the program logic controller based at least in part upon the measured dissolved oxygen content in the influent water stream and the measured nitrate content in the influent water stream, wherein the dosing amount of the particle conditioning agent is adjusted by the program logic controller based at least in part upon the measured turbidity value in the effluent treated water stream, and wherein the oxygenating of the effluent treated water stream is adjusted by the program logic controller based at least in part on the measured dissolved oxygen concentration in the treated effluent stream.
 2. The method of claim 1, further comprising monitoring, using one or more sensors, at least a measured nitrogen concentration in the effluent treated water stream, wherein the dosing amount of the one or more nutrients is adjusted by the program logic controller based additionally, at least in part, on the measured nitrogen concentration in the effluent treated water stream.
 3. The method of claim 2, wherein the program logic controller is configured or programmed to compare the measured nitrogen concentration to a target nitrogen concentration in the effluent treated water stream.
 4. The method of claim 2, further comprising monitoring, using one or more sensors, at least a measured perchlorate concentration in the effluent treated water stream, wherein the adjustment to the dosing amount of the one or more nutrients is based additionally, at least in part, on the measured perchlorate concentration in the effluent treated water stream.
 5. The method of claim 1, wherein said nutrients are at least one of the following: organic carbon based electron donors, phosphorus, nitrogen, or any combination thereof.
 6. The method of claim 5, wherein said nutrients are at least one of the following: acetic acid, phosphoric acid, liquid ammonium sulfate, or any combination thereof.
 7. The method of claim 1, further comprising dosing each of said influent water stream and said effluent treated water stream with a respective dosing amount of hydrogen peroxide to control biomass content.
 8. The method of claim 7, wherein the dosing amount of hydrogen peroxide in the influent water stream and the dosing amount of hydrogen peroxide in the effluent treated water stream are periodically adjusted by the program logic controller.
 9. The method of claim 8, wherein oxygenating the effluent treated water stream comprises dosing the effluent treated water stream with the dosing amount of hydrogen peroxide in the effluent treated water stream.
 10. The method of claim 9, wherein the program logic controller is configured or programmed to compare the measured dissolved oxygen concentration in the treated effluent stream to a target dissolved oxygen concentration in the treated effluent stream.
 11. The method of claim 1, further comprising monitoring, using one or more sensors, at least a measured turbidity value in the treated effluent stream, wherein the dosing amount of the particle conditioning agent is adjusted by the program logic controller based additionally, at least in part, on the measured turbidity value in the treated effluent stream.
 12. The method of claim 11, wherein the program logic controller is configured or programmed to compare the measured turbidity value in the treated effluent stream to a target turbidity value in the treated effluent stream.
 13. The method of claim 1, further comprising measuring a pressure change and turbidity in the anoxic-anaerobic bioreactor and in the aerobic biofilter, and controlling operation of a backwash pump to pump a fluid from a backwash tank to flow through the anoxic-anaerobic bioreactor and the aerobic biofilter to control biomass content based on the measured pressure change and turbidity.
 14. The method of claim 1, wherein the method is performed in a two-stage system consisting of two reactors, wherein a first reactor is the anoxic-anaerobic bioreactor and a second reactor is the aerobic biofilter.
 15. A system for treatment of water that contains contaminants comprising: an anoxic-anaerobic bioreactor in fluid communication with, by way of an influent water conduit, an influent water source containing at least one of a nitrate, perchlorate, chromate, selenate, and a volatile organic chemical; a nutrient dosing unit in fluid communication with said influent water conduit, wherein said nutrient dosing unit is controlled by a program logic controller; a particle conditioning dosing unit in fluid communication with an effluent treated water conduit containing effluent treated water of the anoxic-anaerobic bioreactor connected between said anoxic-anaerobic bioreactor and an aerobic biofilter, wherein said particle conditioning dosing unit is controlled by said program logic controller; an oxygenation unit in communication with the effluent treated water conduit and adapted to oxygenate the effluent treated water between the anoxic-anaerobic bioreactor and the aerobic biofilter, wherein the oxygenation unit is controlled by the program logic controller; a treated effluent conduit containing treated effluent output of said aerobic biofilter; a plurality of in-line sensors positioned to collect data related to the influent water source, effluent treated water, and treated effluent output, the sensors in electronic communication with the program logic controller, including at least a first oxygen analyzer connected to the influent water conduit, a second oxygen analyzer connected to the treated effluent conduit, a first nitrate analyzer connected to the influent water conduit, and a first turbidity sensor connected to the effluent treated water conduit, wherein the program logic controller is programmed to control the nutrient dosing unit and particle conditioning dosing unit based at least partially upon data received from the in-line sensors, wherein the dosing amount of the one or more nutrients is adjusted by the program logic controller based at least in part upon data received from the first oxygen analyzer and the first nitrate analyzer, wherein the dosing amount of the particle conditioning agent is adjusted by the program logic controller based at least in part upon data received from the first turbidity sensor, and wherein the oxygenation unit is adjusted by the program logic controller based at least in part on data received from the second oxygen analyzer.
 16. The system of claim 15, wherein the sensors further comprise: a third oxygen analyzer connected to said effluent treated water conduit; a second nitrate analyzer connected to said effluent treated water conduit; a first pressure sensor transducer connected to said influent water conduit, a second pressure sensor transducer connected to said effluent treated water conduit, and a third pressure sensor transducer connected to said treated effluent conduit; and a second turbidity sensor connected to said treated effluent conduit.
 17. The system of claim 15, wherein the system is a two-stage system consisting of two reactors, wherein a first reactor is the anoxic-anaerobic bioreactor and a second reactor is the aerobic biofilter. 